1. Field of the Invention
The present invention relates to a CMOS type hysteresis characteristic input circuit used in a DC stabilized power supply apparatus.
2. Description of the Related Art
Generally, a DC stabilized power supply apparatus is incorporated into an electronic apparatus. Recently, in order to suppress the power consumption in an OFF operation for the DC stabilized power supply apparatus, an ON/OFF circuit is mounted on the DC stabilized power supply apparatus. Also, in order to avoid the chattering phenomenon in an ON/OFF operation, a hysteresis characteristic input circuit is provided as such an ON/OFF circuit.
A prior art CMOS type hysteresis characteristic input circuit is constructed by two p-channel MOS transistors connected in series between a power supply terminal and a connection point, two n-channel MOS transistors connected in series between the connection point and a ground terminal, an inverter connected to the connection point to generate an output voltage, a switching p-channel MOS transistor connected in parallel to one of the above-mentioned two p-channel MOS transistors, and a switching n-channel MOS transistor connected in parallel to one of the above-mentioned two n-channel MOS transistors. The two p-channel MOS transistors and the two n-channel MOS transistors are controlled by an input voltage, while the switching MOS transistors are complementarily controlled by the output voltage (see: JP-10-154924 A). This will be explained later in detail.